Beyond

Seeing Distant Planets

Astronomy and Physics, Beyond, News

As always, the Hubble Space Telescope is looking to the stars for new exciting sights. Images of swirling galaxies are extremely common. On June 3, 2019, the Hubble Space Telescope released this photo of two exoplanets orbiting a distant star―an incredibly uncommon sight.

The system is called PDS 70 and is located in the constellation Centaurus. Less massive but larger than our sun, the star, also called V1032 Centauri, is a K5 type. K5 stars are cooler and dimmer than our sun. PDS 70 is 370 light-years from the Earth. That’s over 2.17 quadrillion (2,170,000,000,000,000) miles (3.5 quadrillion kilometers)!

In the image below, the white star represents the location of V1032 Centauri. To the left is PDS 70 b and to the right is PDS 70 c.

Exoplanets PDS 70 b and c. Source: ESO and S. Haffert (Leiden Observatory)

Right now, the only way astronomers know how to find planets is by observing the light from the stars. If there is a regular periodic dip in the signal, astronomers can infer that something is passing in front of it. Anything large enough to do this is probably a planet. While this is helpful, a measurement taken from this far leaves lots of room for error.

These planets were first imaged using the Very Large Telescope in Chile. We know that PDS 70 b is 4 to 17 times as massive as Jupiter, while PDS 70 c is 1 to 10 times as massive. The large range in these estimates is a consequence of the lack of precision in the measurement.

Astronomers are rarely able to get images like this because the stars are so big and bright and the planets are small and dim. Star light completely conceals anything coming from a distant planet. In the image above, astronomers cancelled light from the star to reveal the planets.

Once again, the Hubble Space Telescope dazzles us with the cosmos. We will have to wait to see what new sights they excite us with next time!

Another Galaxy Coming to Space Near You!

Astronomy and Physics, Beyond, News

Space continues to dazzle the eye! NASA recently posted this photo of Messier 90. Messier 90, also called NGC 4569, is a spiral galaxy located in the constellation Virgo about 90 million light years away from the Earth.

This image is a composite of light from the infrared, visible, and ultraviolet parts of the spectrum. The black portion of the photo is just a consequence of the camera used.

Source: ESA/Hubble & NASA, W. Sargent et al.

The most fascinating thing about Messier 90 is that the galaxy is moving towards us.

Most galaxies are moving away from us, with a few notable exceptions, including the Andromeda Galaxy. The galaxies move away because the universe is expanding. On a larger scale, everything moves away from us. However, on a more local scale, this expansion isn’t as intense, so galaxies are able to move towards one another.

Astronomers know Messier 90 is moving towards us because it is blue-shifted. The stars that make up galaxies produce photons, the particles of light, in every wavelength of the electromagnetic spectrum. When photons interact with atoms, such as the hydrogen and helium in stars, certain wavelengths are “blacked out” from the spectrum in what are called absorption lines. Absorption lines always occur at the same wavelength for each specific element. Therefore, scientists know exactly where the lines should be. Furthermore, they know exactly which elements a star contains based on these lines alone.

As a source moves towards the observer, the light waves are compressed, making them appear shorter. This causes the absorption lines to move to the shorter wavelength part of the spectrum, or towards the blue part of the visible spectrum. This is why we call them blue-shifted.

The same thing happens when galaxies move away, but instead, the wavelengths get longer. We call this red-shifted. In fact, the large number of red-shifted galaxies is how Edwin Hubble discovered the universe is expanding!

Messier 90 is a member of the Virgo Cluster, a neighbor of our own Local Group. The Virgo Cluster is another small cluster in our supercluster. The Virgo Cluster is thought to be whipping member galaxies around, causing some to be heading towards us. Astronomers think this because Messier 90 is not the only blue-shifted galaxy in the Virgo Cluster. Messier 86 is also blue-shifted!

Messier 90’s center has lots of active star formation, but this does not extend to the edges of the galaxy. Astronomers believe that this is another consequence of the galaxy’s membership in the Virgo Cluster. They theorize that other galaxies in the cluster have stripped Messier 90 of its interstellar material, quenching star formation. In addition, scientists believe that supernovae in the center of the galaxy blew star-forming material out of the galaxy.

A Brief Introduction to Black Holes

Astronomy and Physics, Beyond

On April 10, 2019, astronomers released the first-ever image of a black hole. This image depicts a supermassive black hole in the center of a giant elliptical galaxy known as M87. This image is incredibly important because black holes have never been seen before because they’re, well, black. Black holes do not emit any light (like stars do), nor do they reflect light (light the moon does). This makes them notoriously difficult to detect. In fact, black holes were purely theoretical until the detection of gravitational waves in 2015.

What Are Black Holes?

Black holes were first theorized in the 18th century, but they weren’t truly predicted until 1915 when Einstein published his theory of general relativity. Black holes are a natural prediction of this theory, which simply states that mass bends the four-dimensional spacetime. Not long after, Karl Schwarzschild solved Einstein’s equations and found that for an infinitesimally small point mass, the equations break down when you get near the point mass. This means that physics stops working once you get too close to a black hole. The distance at which physics breaks down is known as the Schwarzschild radius. This radius forms a spherical surface known as the event horizon.

Black holes are an example of extreme physics that form after a massive star dies. This star collapses in on itself and doesn’t stop until the mass is concentrated at an infinitesimally small point in space. This forms a gravitational well so deep that nothing—not even light—can escape. This has one main consequence: we can’t see black holes. What’s more, there didn’t seem to be any way that we could even prove they existed. However, in 2015, scientists had the first physical proof of black holes via gravitational waves. Gravitational waves radiate from high energy collisions. Detectors found evidence of such a collision between two supermassive black holes. Now, for the first time ever, we see a black hole.

Seeing Black Holes

The image shows the black hole in the center of M87, a massive elliptical galaxy. Scientists knew that this galaxy contained an active black hole because of the blue jet seen in the image below.

M87, with a blue jet extending to the bottom right corner. Source: nasa.gov

Scientists used a collaboration of radio telescopes across the globe to see the black hole. They took so much data from their observations that it couldn’t be shared over the internet; they had to manually take the hard drives to one location. After observing the black hole in 2017, it took them two years to compile the data into a single image.

When looking at the image released by the New Horizons Telescope, seen below, one can see a red ring around a dark center. This dark center is the event horizon of the black hole—the point of no return. The red ring is hot, energized, glowing gas. This gas is glowing because it is being flung around the black hole, heating it up. Furthermore, the gas is brighter at the bottom of the image because there, the gas that is moving towards us.

The picture of the black hole taken by the New Horizons Telescope.

Even today, there are tons that we don’t know about black holes. We don’t know how the supermassive black holes in the center of galaxies formed. We don’t know what happens to the information pulled into black holes. We don’t even know how many black holes there are. To say the least, there is a lot of research about black holes coming. Who knows what secrets they keep to themselves. Maybe one day, we’ll find out. Until that day, astronomers will keep on searching the stars for answers.