- Stars move around the center of our Milky Way galaxy just like planets move around stars, bringing their exoplanets along with them. How fast can they travel?
- The fastest-known exoplanet system might be near the center of the Milky Way. Astronomers first discovered it back in 2011 and have now re-observed it.
- The system consists of a possible red dwarf star and super-Neptune exoplanet, 24,000 light-years away. They are moving at an incredible 1.2 million miles per hour (1.9 million kph), and possibly even faster.
Speediest exoplanet?
Stars move around the center of our Milky Way galaxy just as planets move around stars. And now, astronomers have spotted what might be the fastest star – with a planet in tow – found so far. The international team of astronomers said on February 10, 2025, that the planetary system is moving almost twice as fast as our own sun and solar system, at 1.2 million miles per hour, or 1.9 million km per hour. Speedy! The exoplanet system consists of a possible low-mass (red dwarf) star and super-Neptune planet, 24,000 light-years away near the center of the Milky Way.
The researchers also published their peer-reviewed findings in The Astronomical Journal on February 10.
Star and planet or planet and moon?
Astronomers first found the pair of objects back in 2011 in a microlensing survey. When two stars are closely aligned, as seen from Earth, the nearer star acts like a natural cosmic lens, magnifying light from the background star.
Subsequently, they came up with two possible explanations: either a star about 20% as massive as our sun with a planet 29 times more massive than Earth, or a nearer rogue planet about four times the mass of Jupiter with a moon smaller than Earth. But which scenario was the correct one?
The astronomers in the new study used data from the Keck Observatory in Hawaii and the European Space Agency’s Gaia satellite. They reasoned that if it was a rogue planet and moon, they would be effectively invisible in space, with no star to cast light on them. The planet and moon would, therefore, be extremely difficult to detect (although astronomers have indeed found a growing number of rogue planets in recent years).
But if it was a star and planet, then the astronomers could potentially identify the star. The planet itself would still be too faint to see, however, since the pair is so far away.
The astronomers calculated the mass ratio of the two objects, although determining the actual masses is more challenging. Co-author David Bennett, a senior research scientist at the University of Maryland, College Park and NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said:
Determining the mass ratio is easy. It’s much more difficult to calculate their actual masses.
Some cool new science from our group at NASA/Goddard. https://ift.tt/1BE2cRo…
— Sean Terry (@seanterry.bsky.social) 2025-02-10T16:54:33.194Z
Red dwarf and super-Neptune
And to be sure, the astronomers found a good candidate. It’s a low-mass (red dwarf) star about 24,000 light-years away near the galactic bulge in the center of the Milky Way. The researchers compared the location of the star between 2011 and 2021.
Sean Terry is a postdoctoral researcher at the University of Maryland, College Park and Goddard Space Flight Center. He said:
We think this is a so-called super-Neptune world orbiting a low-mass star at a distance that would lie between the orbits of Venus and Earth if it were in our solar system. If so, it will be the first planet ever found orbiting a hypervelocity star.
Could the speediest exoplanet system be moving even faster?
The calculated speed is already really fast. But it’s possible that this planetary system is moving even faster. The speed estimates are of the 2D motion. But if it’s moving toward or away from us – which we don’t know yet – then it might be moving even faster than thought.
If it were to achieve a speed of 1.3 million miles per hour, it could conceivably reach escape velocity and leave our galaxy altogether.
Confirmation still needed
Astronomers still need to confirm that this star is the one that the microlensing signal came from back in 2011. Bennett explained:
To be certain the newly identified star is part of the system that caused the 2011 signal, we’d like to look again in another year and see if it moves the right amount and in the right direction to confirm it came from the point where we detected the signal.
Co-author Aparna Bhattacharya, a research scientist at the University of Maryland, College Park and Goddard Space Flight Center, added:
If high-resolution observations show that the star just stays in the same position, then we can tell for sure that it is not part of the system that caused the signal. That would mean the rogue planet and exomoon model is favored.
NASA’s upcoming Nancy Grace Roman Space Telescope will be able to help find more speedy stars and their planets. It will also conduct a new survey of the galactic bulge in the middle of the Milky Way, where stars are the densest. As Terry noted:
In this case we used MOA [Microlensing Observations in Astrophysics] for its broad field of view and then followed up with Keck and Gaia for their sharper resolution, but thanks to Roman’s powerful view and planned survey strategy, we won’t need to rely on additional telescopes. Roman will do it all.
Other speedy stars
In 2014, astronomers reported finding other sun-like stars moving fast enough to escape our galaxy. And last year, scientists found some other speedy stars that were moving not only fast, but in odd directions.
Bottom line: Astronomers have discovered what might be the speediest exoplanet system known so far. It moves at 1.2 million miles per hour (1.9 million km per hour).
Source: A Candidate High-velocity Exoplanet System in the Galactic Bulge
Read more: These stars are so fast they can escape the Milky Way
Read more: A runaway star moves fast in an unusual direction
The post Speediest exoplanet found near Milky Way center? first appeared on EarthSky.
from EarthSky https://ift.tt/GRWlqPw
- Stars move around the center of our Milky Way galaxy just like planets move around stars, bringing their exoplanets along with them. How fast can they travel?
- The fastest-known exoplanet system might be near the center of the Milky Way. Astronomers first discovered it back in 2011 and have now re-observed it.
- The system consists of a possible red dwarf star and super-Neptune exoplanet, 24,000 light-years away. They are moving at an incredible 1.2 million miles per hour (1.9 million kph), and possibly even faster.
Speediest exoplanet?
Stars move around the center of our Milky Way galaxy just as planets move around stars. And now, astronomers have spotted what might be the fastest star – with a planet in tow – found so far. The international team of astronomers said on February 10, 2025, that the planetary system is moving almost twice as fast as our own sun and solar system, at 1.2 million miles per hour, or 1.9 million km per hour. Speedy! The exoplanet system consists of a possible low-mass (red dwarf) star and super-Neptune planet, 24,000 light-years away near the center of the Milky Way.
The researchers also published their peer-reviewed findings in The Astronomical Journal on February 10.
Star and planet or planet and moon?
Astronomers first found the pair of objects back in 2011 in a microlensing survey. When two stars are closely aligned, as seen from Earth, the nearer star acts like a natural cosmic lens, magnifying light from the background star.
Subsequently, they came up with two possible explanations: either a star about 20% as massive as our sun with a planet 29 times more massive than Earth, or a nearer rogue planet about four times the mass of Jupiter with a moon smaller than Earth. But which scenario was the correct one?
The astronomers in the new study used data from the Keck Observatory in Hawaii and the European Space Agency’s Gaia satellite. They reasoned that if it was a rogue planet and moon, they would be effectively invisible in space, with no star to cast light on them. The planet and moon would, therefore, be extremely difficult to detect (although astronomers have indeed found a growing number of rogue planets in recent years).
But if it was a star and planet, then the astronomers could potentially identify the star. The planet itself would still be too faint to see, however, since the pair is so far away.
The astronomers calculated the mass ratio of the two objects, although determining the actual masses is more challenging. Co-author David Bennett, a senior research scientist at the University of Maryland, College Park and NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said:
Determining the mass ratio is easy. It’s much more difficult to calculate their actual masses.
Some cool new science from our group at NASA/Goddard. https://ift.tt/1BE2cRo…
— Sean Terry (@seanterry.bsky.social) 2025-02-10T16:54:33.194Z
Red dwarf and super-Neptune
And to be sure, the astronomers found a good candidate. It’s a low-mass (red dwarf) star about 24,000 light-years away near the galactic bulge in the center of the Milky Way. The researchers compared the location of the star between 2011 and 2021.
Sean Terry is a postdoctoral researcher at the University of Maryland, College Park and Goddard Space Flight Center. He said:
We think this is a so-called super-Neptune world orbiting a low-mass star at a distance that would lie between the orbits of Venus and Earth if it were in our solar system. If so, it will be the first planet ever found orbiting a hypervelocity star.
Could the speediest exoplanet system be moving even faster?
The calculated speed is already really fast. But it’s possible that this planetary system is moving even faster. The speed estimates are of the 2D motion. But if it’s moving toward or away from us – which we don’t know yet – then it might be moving even faster than thought.
If it were to achieve a speed of 1.3 million miles per hour, it could conceivably reach escape velocity and leave our galaxy altogether.
Confirmation still needed
Astronomers still need to confirm that this star is the one that the microlensing signal came from back in 2011. Bennett explained:
To be certain the newly identified star is part of the system that caused the 2011 signal, we’d like to look again in another year and see if it moves the right amount and in the right direction to confirm it came from the point where we detected the signal.
Co-author Aparna Bhattacharya, a research scientist at the University of Maryland, College Park and Goddard Space Flight Center, added:
If high-resolution observations show that the star just stays in the same position, then we can tell for sure that it is not part of the system that caused the signal. That would mean the rogue planet and exomoon model is favored.
NASA’s upcoming Nancy Grace Roman Space Telescope will be able to help find more speedy stars and their planets. It will also conduct a new survey of the galactic bulge in the middle of the Milky Way, where stars are the densest. As Terry noted:
In this case we used MOA [Microlensing Observations in Astrophysics] for its broad field of view and then followed up with Keck and Gaia for their sharper resolution, but thanks to Roman’s powerful view and planned survey strategy, we won’t need to rely on additional telescopes. Roman will do it all.
Other speedy stars
In 2014, astronomers reported finding other sun-like stars moving fast enough to escape our galaxy. And last year, scientists found some other speedy stars that were moving not only fast, but in odd directions.
Bottom line: Astronomers have discovered what might be the speediest exoplanet system known so far. It moves at 1.2 million miles per hour (1.9 million km per hour).
Source: A Candidate High-velocity Exoplanet System in the Galactic Bulge
Read more: These stars are so fast they can escape the Milky Way
Read more: A runaway star moves fast in an unusual direction
The post Speediest exoplanet found near Milky Way center? first appeared on EarthSky.
from EarthSky https://ift.tt/GRWlqPw
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