Billions of Celestial Objects Revealed in Gargantuan Survey of the Milky Way
A colossal astronomical tapestry displays the majesty of the Milky Way in unprecedented detail.
Credit: DECaPS2/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA Image processing: M. Zamani & D. de Martin (NSF’s NOIRLab)
Cambridge, MA – A new astronomical survey is a portrait of gargantuan proportions. It shows the staggering number of stars bristling among the wispy bands of dust in our home galaxy, the Milky Way. The heart of our galaxy — the central bulge of bright blue stars that also contains the supermassive black hole Sagittarius A* — is at the left side of this panorama.
This galactic panorama was captured by the Dark Energy Camera (DECam) instrument on the Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory (CTIO), a Program of NSF’s NOIRLab. CTIO is a constellation of international astronomical telescopes perched atop Cerro Tololo in Chile at an altitude of 2,200 meters (7,200 feet). CTIO’s lofty vantage point gives astronomers an unrivaled view of the southern celestial hemisphere, which allowed DECam to capture the southern Galactic plane in such detail.
Astronomers have released a gargantuan survey of the galactic plane of the Milky Way. The new dataset contains a staggering 3.32 billion celestial objects — arguably the largest such catalog so far. The survey is here reproduced in 4000-pixels resolution to be accessible on smaller devices.
Credit: DECaPS2/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA/E. Slawik Image processing: M. Zamani & D. de Martin (NSF’s NOIRLab)
The data used to create this survey originate from the second release of the Dark Energy Camera Plane Survey (DECaPS2), a survey of the plane of the Milky Way as seen from the southern sky taken at optical and near-infrared wavelengths. The new data is described today in The Astrophysical Journal Supplement .
“One of the main reasons for the success of DECaPS2 is that we simply pointed at a region with an extraordinarily high density of stars and were careful about identifying sources that appear nearly on top of each other,” says Andrew Saydjari, a graduate student at Harvard University, researcher at the Center for Astrophysics | Harvard & Smithsonian, and lead author of the paper. “Doing so allowed us to produce the largest catalog ever from a single camera, in terms of the number of objects observed.”
The first trove of data from DECaPS was released in 2017. With the addition of the new data, the survey now covers 6.5 percent of the night sky and spans a staggering 130-degrees in length. While it might sound modest, this equates to 13,000 times the angular area of the full Moon.
“When combined with images from Pan-STARRS 1, DECaPS2 completes a 360-degree panoramic view of the Milky Way’s disk and additionally reaches much fainter stars,” says Edward Schlafly, a researcher at the AURA-managed Space Telescope Science Institute and a co-author of the paper describing DECaPS2 published in The Astrophysical Journal Supplement . “With this new survey, we can map the three-dimensional structure of the Milky Way’s stars and dust in unprecedented detail.”
Gathering the data required to cover this much of the night sky was a Herculean task; the DECaPS2 survey identified 3.32 billion objects from over 21,400 individual exposures. Its two-year run, which involved about 260 hours of observations, produced more than 10 terabytes of data.
Most of the stars and dust in the Milky Way are located in its spiral disk — the bright band stretching across this image. While this profusion of stars and dust makes for beautiful images, it also makes the galactic plane challenging to observe. The dark tendrils of dust seen threading through this image absorb starlight and blot out fainter stars entirely, and the light from diffuse nebulae interferes with any attempts to measure the brightness of individual objects. Another challenge arises from the sheer number of stars, which can overlap in the image and make it difficult to disentangle individual stars from their neighbors.
Despite the challenges, astronomers delved into the galactic plane to gain a better understanding of our Milky Way. By observing at near-infrared wavelengths, they were able to peer past much of the light-absorbing dust. The researchers also used an innovative data-processing approach, which allowed them to better predict the background behind each star. This helped to mitigate the effects of nebulae and crowded star fields on such large astronomical images, ensuring that the final catalog of processed data is more accurate.
“Since my work on the Sloan Digital Sky Survey two decades ago, I have been looking for a way to make better measurements on top of complex backgrounds,” said Douglas Finkbeiner, a professor at the Center for Astrophysics, co-author of the paper, and principal investigator behind the project. “This work has achieved that and more!”
“This is quite a technical feat. Imagine a group photo of over three billion people and every single individual is recognizable!” says Debra Fischer, division director of Astronomical Sciences at NSF. “Astronomers will be poring over this detailed portrait of more than three billion stars in the Milky Way for decades to come. This is a fantastic example of what partnerships across federal agencies can achieve.”
Interactive access to the imaging with panning/zooming inside of a web-browser is available from the LegacySurveyViewer, the World Wide Telescope and Aladin.
The DECaPS2 dataset is available to the entire scientific community and is hosted by NOIRLab’s Astro Data Lab, which is part of the Community Science and Data Center.
DECam was originally built to carry out the Dark Energy Survey, which was conducted by the Department of Energy and the U.S. National Science Foundation between 2013 and 2019.
The DECaPS2 team is composed of A. K. Saydjari (Harvard University and the Center for Astrophysics | Harvard & Smithsonian), E. F. Schlafly (Space Telescope Science Institute), D. Lang (Perimeter Institute for Theoretical Physics and University of Waterloo), A. M. Meisner (NSF’s NOIRLab), G. M. Green (Max Planck Institute for Astronomy), C. Zucker (Space Telescope Science Institute and the Center for Astrophysics | Harvard & Smithsonian), I. Zelko (Canadian Institute of Theoretical Astrophysics – University of Toronto), J. S. Speagle (University of Toronto), T. Daylan (Princeton University), A. Lee (Bill & Melinda Gates Foundation), F. Valdes (NSF’s NOIRLab), D. Schlegel (Lawrence Berkeley National Laboratory), and D. P. Finkbeiner (Harvard University and the Center for Astrophysics | Harvard & Smithsonian).
About NOIRLab
NSF’s NOIRLab (National Optical-Infrared Astronomy Research Laboratory), the U.S. center for ground-based optical-infrared astronomy, operates the international Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), Kitt Peak National Observatory (KPNO), Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and Vera C. Rubin Observatory (in cooperation with DOE’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research on Iolkam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence that these sites have to the Tohono O’odham Nation, to the Native Hawaiian community, and to the local communities in Chile, respectively.
About the Center for Astrophysics | Harvard & Smithsonian
The Center for Astrophysics | Harvard & Smithsonian is a collaboration between Harvard and the Smithsonian designed to ask—and ultimately answer—humanity’s greatest unresolved questions about the nature of the universe. The Center for Astrophysics is headquartered in Cambridge, MA, with research facilities across the U.S. and around the world.
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Introduction on background medium theory about celestial body motion orbit and foundation of fractional-dimension calculus about self-fractal measure calculation
In this paper, by discussing the basic hypotheses about the continuous orbit and discrete orbit in two research directions of the background medium theory for celestial body motion, the concrete equation forms and their summary of the theoretic frame of celestial body motion are introduced. Future more, by discussing the general form of Binet’s equation of celestial body motion orbit and it’s solution of the advance of the perihelion of planets, the relations and differences between the continuous orbit theory and Newton’s gravitation theory and Einstein’s general relativity are given. And by discussing the fractional-dimension expanded equation for the celestial body motion orbits, the concrete equations and the prophesy data of discrete orbit or stable orbits of celestial bodies which included the planets in the Solar system, satellites in the Uranian system, satellites in the Earth system and satellites obtaining the Moon obtaining from discrete orbit theory are given too. Especially, as the preliminary exploration and inference to the gravitation curve of celestial bodies in broadly range, the concept for the ideal black hole with trend to infinite in mass density difficult to be formed by gravitation only is explored. By discussing the position hypothesis of fractional-dimension derivative about general function and the formula form the hypothesis of fractional-dimension derivative about power function, the concrete equation formulas of fractional-dimension derivative, differential and integral are described distinctly further, and the difference between the fractional-dimension derivative and the fractional-order derivative are given too. Subsequently, the concrete forms of measure calculation equations of self-similar fractal obtaining by based on the definition of form in fractional-dimension calculus about general fractal measure are discussed again, and the differences with Hausdorff measure method or the covering method at present are given. By applying the measure calculation equations, the measure of self-similar fractals which include middle-third Cantor set, Koch curve, Sierpinski gasket and orthogonal cross star are calculated and analyzed.
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Keywords:
- orbit of celestial body motion /
- background medium theory /
- continuous orbit /
- discrete orbit /
- self-similar fractal measure /
- fractional-dimension calculus /
- fractional-dimension derivative
Newly discovered planet has longest orbit yet detected by the TESS mission
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Caption :
An artist’s rendition of the two planets and star in the TOI-4600 system
Credits :
Credit: Tedi Vick
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Of the more than 5,000 planets known to exist beyond our solar system, most orbit their stars at surprisingly close range. More than 80 percent of confirmed exoplanets have orbits shorter than 50 days, placing these toasty worlds at least twice as close to their star as Mercury is to our sun — and some, even closer than that.
Astronomers are starting to get a general picture of these planets’ formation, evolution, and composition. But the picture is much fuzzier for planets with longer orbital periods. Far-out worlds, with months- to years-long orbits, are more difficult to detect, and their properties have therefore been trickier to discern.
Now, the list of long-period planets has gained two entries. Astronomers at MIT, the University of New Mexico, and elsewhere have discovered a rare system containing two long-period planets orbiting TOI-4600, a nearby star that is 815 light years from Earth.
The team discovered that the star hosts an inner planet with an orbit of 82 days, similar to that of Mercury, while a second outer planet circles every 482 days, placing it somewhere between the orbits of Earth and Mars.
The discovery was made using data from NASA’s Transiting Exoplanet Survey Satellite, or TESS — an MIT-led mission that monitors the nearest stars for signs of exoplanets. The new, farther planet has the longest period that TESS has detected to date. It is also one of the coldest, at about -117 degrees Fahrenheit, while the inner planet is a more temperate 170 degrees Fahrenheit.
Both planets are likely gas giants, similar to Jupiter and Saturn, though the composition of the inner planet may be more of a mix of gas and ice. The two planets bridge the gap between “hot Jupiters” — the toasty, short-orbit planets that make up the majority of exoplanet discoveries — and the much colder, longer-period gas giants in our solar system.
“These longer-period systems are a comparatively unexplored range,” says team member Katharine Hesse, a technical staff member at MIT’s Kavli Institute for Astrophysics and Space Research. “As we’re trying to see where our solar system falls in comparison to the other systems we’ve found out there, we really need these more edge-case examples to better understand that comparison. Because a lot of systems we have found don’t look anything like our solar system.”
Hesse and her colleagues, including lead author Ismael Mireles, a graduate student at the University of New Mexico (UNM), have published their results today in Astrophysical Journal Letters.
Patch work
TESS monitors the nearest stars for signs of exoplanets by pointing at a patch of the sky and continuously measuring the brightness of stars in that sector for 30 days, before swiveling to the next patch. Scientists use “pipelines,” or algorithmic searches, to comb through the measurements for dips in brightness that could have been caused by a planet passing in front of its star.
In 2020, one pipeline picked up a possible transit from a star in the northern sky, close to the constellation Draco. The star was categorized as TOI-4600 (a TESS Object of Interest). The initial transit was studied in detail by the TESS Single Transit Planet Candidate Working Group, a team of scientists at MIT, UNM, and elsewhere who look for signs of longer-period planets in single-transit events.
“For missions like TESS, where it only looks at each region of the sky for 30 days, you really need to stack up the number of observations to be able to get enough data to find planets with orbits longer than a month,” Hesse notes.
The group looked for the star in other sectors of TESS data and eventually identified three more transits, similar to the first. From these four events, the scientists were able to determine that the source was a planet — TOI-4600b — with a relatively long 82-day orbit. The team also picked up a fifth transit, though it was out of sync with the other signals. They wondered: Could the transit be from another star temporarily eclipsing the first? Or could it be a second orbiting planet?
Giants in the sky
In 2021, when Mireles joined the group, he took up where the team left off, looking for more observations from TESS that would explain the last, puzzling transit.
“With each sector of data that came down, I would look to see if there was a second transit, and in the first five sectors, there wasn’t,” Mireles recalls. “Then, in July of last year, we saw something.”
Actually, they saw two things: one transit that appeared in the same 82-day cycle, which further confirmed the existence of a long-orbiting planet; and a second transit, which was detected 964 days after the previous, out-of-sync transit. These last two transits were similar in depth, or the amount of light that was dimmed, suggesting that both were produced by a single object that was orbiting the star, either every 964 days, or every 482 days. After all, the team reasoned, TESS simply could have not been looking in the star’s direction to catch the planet crossing at the 482-day mark. The team used a model to simulate what a planet would look like with both orbital periods, and concluded that the 482-day orbit was more likely.
To further confirm they had identified two long-period planets, the researchers focused in on the star using multiple ground-based telescopes. These observations helped the team rule out false-positive scenarios, such as a second star eclipsing the main star. In the end, they concluded that the star indeed hosts two long-period planets: TOI-4600b, a warm, Jupiter-like giant; and TOI-4600c, a frosty, icier giant, and the longest-period planet detected by TESS to date.
“It’s relatively rare that we see two giant planets in a system,” Hesse offers. “We’re used to seeing hot Jupiters that are close in to their stars, and we usually don’t find companions to them, let alone giant companions. This system is a more unique configuration.”
The distance between the two planets, which is about the same as the space between Mercury and Mars, implies there could be other planets in the system.
“We want to see if there’s evidence for more planets,” Mireles says. “There’s definitely a lot of room for potential planets, either closer in, or further out. And we show that TESS is capable of finding both warm and cold Jupiters.”
This research was supported, in part, by NASA.
