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Nasa Science - Blog Posts
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Mushroom fact of the Week!
Lichens are extremely durable. In 2005 NASA sent lichen to space to test how it stood up in the freezing cold vacuum. It was left outside in space for a period of time, and within 24 hours of rehydration had resumed all normal photosynthetic activity
Cross section of Xanthoria elegans, one of the two lichens sent to space!
Star Trails taken by Rob on February 24 2024
Star trails are photographs taken over long exposures, where the rotation of the Earth causes the stars to appear as arcs in the sky instead of points. The Earth rotates around its axis every 23 hours and 56 minutes.
Typically, star trails are focused on Polaris in the northern hemisphere, but I found this photo unique because it opted for a different composition. It also really highlights how dense the sky is with stars.
It begs the question, why isn't the sky infinitely bright with infinite stars? This is actually the observation that helped cosmologists find theories for the age of the universe. For a young universe, not enough time has passed for the light from incredibly distant stars to reach us, leading to the dark sky we see when we look up at night.
The Large Magellanic Cloud taken by Rory Broesder on Februrary 18 2023
The LMC is a satellite galaxy to the Milky Way, set to collide in 2.4 billion years. It is an easily observable object from the southern hemisphere and is the fourth brightest galaxy in the local group. Within this galaxy is the Tarantula Nebula, a very active star forming region.
It was once a barred spiral galaxy before it was disrupted through tidal interactions with the Milky Way galaxy and Small Magellanic Cloud. In fact, there is a bridge of hot gas showing the connection between the LMC and SMC which is also an active star forming region.
The LMC is one of around sixty other satellite galaxies orbiting the Milky Way.
Vela Supernova Remnant taken on February 6 2021 by jeff2011 on Astrobin
The supernova remnant resides within the Vela constellation, having exploded over ten thousand years ago. It is the closes supernova remnant to Earth. Observational data from this remnant provided proof that supernova’s can produce neutron stars.
Supernovas occur at the end of a star’s life. Stars with mass over eight solar masses finish burning the hydrogen in their core and become a red supergiant. Successive fusion then occurs until the core contains iron. Fusion can no longer occur at iron since it is not energetically favorable. Gravity then takes over leading to a supernova explosion— expelling a huge amount of stellar material.
Neutron stars can form as a result of this, as protons and electrons collide to combine into neutrons. The neutron stars are stable by neutron degeneracy pressure. This pressure is caused the Pauli Exclusion principal which prevents neutrons from having the same positions.
NGC 2403 taken by John C. Yu on January 30 2024
NGC 2403 is a intermediate spiral galaxy. There are typically two types of spiral galaxies: barred and regular spirals. This galaxy falls between the two, denoted as SAB.
The bar in spiral galaxies forms due to gravitational instability. However, this bar can help with star formation as it funnels material to the center of the galaxy.
Interactions with neighboring galaxies or having greater instability can lead to a greater bar shape in the galaxy. However, dark matter halos also play a big role in having the opposite effect, often preventing the bar from forming. These combined factors lead to the median shape of this galaxy.
Intermediate spiral galaxies can eventually evolve into either regular spiral galaxies or barred spiral galaxies, but we won't be there to see the final form of NGC 2403.
Messier 66 taken by Hubble Space Telescope on January 28 2021
In this picture, it showcases the star forming regions of the galaxies, which can be seen in red. Star forming regions are vulnerable to disturbances, which can cause the gas in the interstellar medium to collapse into dense clumps of material. These are called protostars.
During the formation of these protostars, gravitational energy is converted into thermal energy. If there is enough thermal energy produced, it is enough to spark nuclear fusion. The star then joins the main sequence.
Due to nature of the star forming regions, it often yields the creation of star clusters, since many stars are being created in close proximity. Large stars especially can emit radiation and produce stellar winds, which pushes the star away from these regions.