Imaging low-mass planets within the habitable zone of α Centauri
Giant exoplanets on wide orbits have been directly imaged around young stars. If the thermal background in the mid-infrared can be mitigated, then exoplanets with lower masses can also be imaged. Here we present a ground-based mid-infrared observing approach that enables imaging low-mass temperate exoplanets around nearby stars, and in particular within the closest stellar system, α Centauri. Based on 75–80% of the best quality images from 100 h of cumulative observations, we demonstrate sensitivity to warm sub-Neptune-sized planets throughout much of the habitable zone of α Centauri A. This is an order of magnitude more sensitive than state-of-the-art exoplanet imaging mass detection limits. We also discuss a possible exoplanet or exozodiacal disk detection around α Centauri A. However, an instrumental artifact of unknown origin cannot be ruled out. These results demonstrate the feasibility of imaging rocky habitable-zone exoplanets with current and upcoming telescopes.
Is It a Planet? Astronomers Spy Promising Potential World around Alpha Centauri
For the first time ever, astronomers may have glimpsed light from a world in a life-friendly orbit around another star.
The planet candidate remains unverified and formally unnamed, little more than a small clump of pixels on a computer screen, a potential signal surfacing from a sea of background noise. If proved genuine, the newly reported find would in most respects not be particularly remarkable: a “warm Neptune” estimated to be five to seven times larger than Earth, the sort of world that galactic census-takers such as NASA’s Kepler and Transiting Exoplanet Survey Satellite missions have revealed to be common throughout the Milky Way. But even though it would be shrouded in gas and essentially bereft of any surface to stand on, its distance from its star would place it in the so-called “habitable zone” where liquid water could exist. No other planet has been directly seen in this starlight-drenched region around any other star, because of the associated glare. And this world’s celestial coordinates would be straight out of astronomers’ wildest dreams—it would orbit a near-twin of the sun called Alpha Centauri A, which also happens to be a member of a triple-star system that, at just shy of 4.5 light-years away, is the closest one to our own.
Hope, the United Arab Emirates’ First Mission to Mars
- Hope is a United Arab Emirates mission to Mars that arrived in orbit on 9 February 2021.
- The mission will build a complete picture of Mars’ climate, helping scientists better understand what Mars was like when its atmosphere could have supported life.
- Hope is the Arab world’s first mission to another planet. More countries exploring our solar system means more discoveries and opportunities for global collaboration.
Giant radio telescope reaches milestone en route to construction start
The Square Kilometre Array has been a dream of radio astronomers for nearly 3 decades. Today, the project officially becomes the Square Kilometre Array Observatory (SKAO). Last month, a treaty ratified by six of the project’s member governments came into force. The project’s governing council—with delegates from the six ratifying nations and 10 others as observers—meets (virtually) for the first time and conjures the SKAO into existence.
The aim is to build the world’s biggest radio observatory, originally envisioned as having 1 square kilometer of collecting area. With such a photon-gathering potential, the telescope could see the universe’s very first stars and galaxies, study the effects of cosmic magnetism and gravity, and listen for the signs of alien civilizations.
The €2 billion project is split across two sites: 130,000 wire antennas in the Western Australian desert to collect low-frequency signals, and 130 dishes in South Africa for higher frequencies, which will be added to that country’s existing 64-dish MeerKAT array. In both cases, the receivers are arranged in dense cores with arms extending out hundreds of kilometers. By digitally combining the signals picked up by many widely spaced receivers, the array gains both sharp resolution and exquisite sensitivity.
With the design vetted and approved, and other governments preparing to join, the SKAO can now get on with inviting bids from companies to build the observatory, with a view to starting construction later this year.
Curious spiral spotted by ALMA around red giant star R Sculptoris (data visualisation)
Observations using the Atacama Large Millimeter/submillimeter Array (ALMA) have revealed an unexpected spiral structure in the material around the old star R Sculptoris. This feature has never been seen before and is probably caused by a hidden companion star orbiting the star. This slice through the new ALMA data reveals the shell around the star, which shows up as the outer circular ring, as well as a very clear spiral structure in the inner material.
Measurement of the spin of the M87 black hole from its observed twisted light
We present the first observational evidence that light propagating near a
rotating black hole is twisted in phase and carries orbital angular
momentum (OAM). This physical observable allows a direct measurement of
the rotation of the black hole. We extracted the OAM spectra from the
radio intensity data collected by the Event Horizon Telescope from
around the black hole M87* by using wavefront reconstruction and phase
recovery techniques and from the visibility amplitude and phase maps.
This method is robust and complementary to black hole shadow circularity
analyses. It shows that the M87* rotates clockwise with an estimated
rotation parameter a = 0.90 ± 0.05 with an ∼95 per cent confidence level (c.l.) and an inclination i = 17° ± 2°, equivalent to a magnetic arrested disc with an inclination i = 163° ± 2°. From our analysis, we conclude that, within a 6σ c.l., the M87* is rotating.
An expanse of cosmic dust, stars and nebulae along
the plane of our Milky Way galaxy form a beautiful ring in
this projected all-sky view.
The creative panorama covers the entire
galaxy visible
from planet Earth,
an ambitious 360 degree mosaic that took two years to complete.
Northern hemisphere sites in western China and southern hemisphere
sites in New Zealand were used
to collect the image data.
Like a glowing jewel set in the milky ring,
the bulge of the
galactic center,
is at the very top.
Bright planet Jupiter is the beacon just above the central bulge
and left of red giant star
Antares.
Along the plane and almost 180 degrees from the galactic center,
at the bottom of the ring is the area
around Orion,
denizen of the northern hemisphere’s evening winter skies.
In this projection the ring of the Milky Way encompasses two notable
galaxies in southern skies, the large and small
Magellanic clouds.
Using space-VLBI to probe gravity around Sgr A*
The Event Horizon Telescope (EHT) will soon provide the first high-resolution images of the Galactic Centre supermassive black hole (SMBH) candidate Sagittarius A* (Sgr A*), enabling us to probe gravity in the strong-field regime. Besides studying the accretion process in extreme environments, the obtained data and reconstructed images could be used to investigate the underlying spacetime structure. In its current configuration, the EHT is able to distinguish between a rotating Kerr black hole and a horizon-less object like a boson star. Future developments can increase the ability of the EHT to tell different spacetimes apart. We investigate the capability of an advanced EHT concept, including an orbiting space antenna, to image and distinguish different spacetimes around Sgr A*. We use GRMHD simulations of accreting compact objects (Kerr and dilaton black holes, as well as boson stars) and compute their radiative signatures via general relativistic radiative transfer calculations. To facilitate comparison with upcoming and future EHT observations we produce realistic synthetic data including the source variability, diffractive and refractive scattering while incorporating the observing array, including a space antenna. From the generated synthetic observations we dynamically reconstructed black hole shadow images using regularised Maximum Entropy methods. We employ a genetic algorithm to optimise the orbit of the space antenna with respect to improved imaging capabilities and u-v-plane coverage of the combined array (ground array and space antenna and developed a new method to probe the source variability in Fourier space. The inclusion of an orbiting space antenna improves the capability of the EHT to distinguish the spin of Kerr black holes and dilaton black holes based on reconstructed radio images and complex visibilities.
Kepler-411 differential rotation from three transiting planets
The differential rotation of the Sun is a crucial ingredient of the dynamo
theory responsible for the generation of its magnetic field. Currently, the
rotation profile of a star that hosts one or more transiting planets can be
estimated. By detecting the same spot in a later transit, it is possible to
infer the stellar rotation period at that latitude. In this work, we apply for
the first time transit spot mapping to determine the differential rotation of
Kepler-411, a K2V-type star with an average rotation period of 10.52 days,
radius of 0.79 R⊙ and mass of 0.83 M⊙. Kepler-411 hosts at least
four planets, the inner planet is a super-Earth with a radius of 1.88
R⊕ and an orbital period of 3.0051 days, whereas the two larger
transiting planets are mini Neptunes with radii of 3.27 and 3.31 R⊕,
and periods of 7.834435 and 58.0204 days, respectively. Their orbits are such
that they transit the star at latitudes of -11∘, -21∘, and
-49∘. Analysis of the transit light curves of the three planets
resulted in the detection of a total of 198 spots. For each transit latitude,
the rotation period of the star was estimated and the differential rotation
pattern estimated independently. Then a solar like differential rotation
profile was fit to the three rotation periods at the distinct latitudes, the
result agreed extremely well with the previous ones, resulting in a
differential shear of 0.0500±0.0006 rd/d or a relative differential
rotation of 8.4±0.1\%.
Explore every gravitational wave event spotted so far
Throughout the universe, violent collisions of cosmic beasts such as black holes wrench the fabric of spacetime, producing ripples called gravitational waves. For most of history, humans have been oblivious to those celestial rumbles. Today, we’ve detected scores of them.
The first came in 2015, when scientists with the Advanced Laser Interferometer Gravitational-Wave Observatory, or LIGO, spotted gravitational waves spawned from the merger of two black holes. That event rattled the bones of the cosmos — shaking the underlying structure of space and time. The detection also stirred up astronomy, providing a new way to observe the universe, and verified a prediction of Albert Einstein’s general theory of relativity (SN: 2/11/16).
But like a lone ripple in a vast sea, a single detection can tell scientists only so much. Now, LIGO and its partner observatory Advanced Virgo have collected 50 sets of gravitational waves. Most of these spacetime ripples resulted from two black holes spiraling inward before colliding. Some arose from collisions of dense stellar corpses called neutron stars. Two collisions involve celestial bodies that can’t be confidently identified, hinting that scientists may have spotted the first merger of a neutron star with a black hole (SN: 6/23/20).
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