Tag Archives: space

Perihelion 2020: The Earth is Closest to the Sun Today

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The Earth reached its Perihelion today at 7:48 UTC, which is 2:48 AM Eastern Standard Time. This is the point in the planet’s orbit where it comes closest to the Sun.

This annual event is due to the elliptical shape of the Earth’s orbit and the off-centered position of the Sun inside that path. The exact date of the Perihelion differs from year to year, but it’s usually in early January – winter in the northern hemisphere. The Earth will be furthest from the Sun in July.

While the planet’s distance from the Sun is not responsible for the seasons, it does influence their length. As a function of gravity, the closer the planet is to the Sun, the faster it moves. Today, the Earth is 147.1 million kilometers (91.4 million miles) away from the Sun. That is approximately 5 million kilometers (3 million miles) closer than it will be in early July. This position allows the planet to speed up by about one-kilometer per second. As a result, winter in the northern hemisphere is about five days shorter than summer.

The word, perihelion, is Greek for “near sun”.

Earth’s Perihelion and Aphelion. Credit: Time and Date.com

The Science Behind the Autumnal Equinox

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Today is the Autumnal Equinox, the first day of fall in the northern hemisphere. The new season officially began at 7:50 UTC, which is 3:50 AM Eastern Daylight Time.

The astronomical seasons, as opposed to the meteorological seasons, are a product of Earth’s axial tilt – a 23.5° angle – and the movement of the planet around the sun. During the autumn months, the Earth’s axis is tilted neither toward nor away from the sun. This position distributes the sun’s energy equally between the northern and southern hemispheres.

Since the summer solstice in June, the arc of the sun’s apparent daily passage across the sky has been sinking and daylight hours have been decreasing. Today, the sun appears directly overhead at the equator and we have approximately equal hours of day and night. The word “equinox” is derived from Latin and means “equal night”.

Transitioning from summer to winter, autumn is also a season of falling temperatures. According to NOAA, the average high temperature in most US cities drops about 10°F between September and October.

Earth’s solstices and equinoxes. Image Credit: NASA

Aphelion 2019: Earth Farthest from Sun Today

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The Earth will reach its farthest point from the Sun today – an event known as the aphelion. It will officially take place at 22:10 UTC, which is 6:10 PM Eastern Daylight Time.

This annual event is a result of the elliptical shape of the Earth’s orbit and the slightly off-centered position of the Sun inside that path. The exact date of the Aphelion differs from year to year, but it’s usually in early July – summer in the northern hemisphere.

While the planet’s distance from the Sun is not responsible for the seasons, it does influence their length. As a function of gravity, the closer the planet is to the Sun, the faster it moves. Today, Earth is about 152 million kilometers (94 million miles) away from the Sun. That is approximately 5 million kilometers (3 million miles) further than during the perihelion in early January. That means the planet will move more slowly along its orbital path than at any other time of the year. As a result, summer is elongated by a few days in the northern hemisphere.

The word, aphelion, is Greek for “away from the sun”.

Earth’s Perihelion and Aphelion. Credit: Time and Date.com

Perihelion 2019: The Earth is Closest to the Sun Today

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The Earth reached its Perihelion today at 5:20 UTC, which is 12:20 AM Eastern Standard Time. This is the point in the planet’s orbit where it comes closest to the Sun.

This annual event is due to the elliptical shape of the Earth’s orbit and the off-centered position of the Sun inside that path. The exact date of the Perihelion differs from year to year, but it’s usually in early January – winter in the northern hemisphere. The Earth will be furthest from the Sun in July.

While the planet’s distance from the Sun is not responsible for the seasons, it does influence their length. As a function of gravity, the closer the planet is to the Sun, the faster it moves. Today, the Earth is 147.1 million kilometers (91.4 million miles) away from the Sun. That is approximately 5 million kilometers (3 million miles) closer than it will be in early July. This position allows the planet to speed up by about one-kilometer per second. As a result, winter in the northern hemisphere is about five days shorter than summer.

The word, perihelion, is Greek for “near sun”.

Earth’s Perihelion and Aphelion. Credit: Time and Date.com

What Causes the Autumnal Equinox

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Today is the Autumnal Equinox, the first day of fall in the northern hemisphere. The new season officially begins at 9:54 PM Eastern Daylight Time.

The astronomical seasons, as opposed to the meteorological seasons,  are a product of Earth’s axial tilt – a 23.5° angle – and the movement of the planet around the sun. During the autumn months, the Earth’s axis is tilted neither toward nor away from the sun. This position distributes the sun’s energy equally between the northern and southern hemispheres.

Since the summer solstice in June, the arc of the sun’s apparent daily passage across the sky has been sinking and daylight hours have been decreasing. Today, the sun appears directly overhead at the equator and we have approximately equal hours of day and night. The word “equinox” is derived from Latin and means “equal night”.

Transitioning from summer to winter, autumn is also a season of falling temperatures. According to NOAA, the average high temperature in most US cities drops about 10°F between September and October.

Earth’s solstices and equinoxes. Image Credit: NASA

Aphelion 2018: Earth Farthest from Sun Today

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The Earth will reach its farthest point from the Sun today – an event known as the aphelion. It will officially take place at 16:46 UTC, which is 12:46 PM Eastern Daylight Time.

This annual event is a result of the elliptical shape of the Earth’s orbit and the slightly off-centered position of the Sun inside that path. The exact date of the Aphelion differs from year to year, but it’s usually in early July – summer in the northern hemisphere.

While the planet’s distance from the Sun is not responsible for the seasons, it does influence their length. As a function of gravity, the closer the planet is to the Sun, the faster it moves. Today, Earth is about 152 million kilometers (94 million miles) away from the Sun. That is approximately 5 million kilometers (3 million miles) further than during the perihelion in early January. That means the planet will move more slowly along its orbital path than at any other time of the year. As a result, summer is elongated by a few days in the northern hemisphere.

The word, aphelion, is Greek for “away from the sun”.

Earth is farthest from the Sun during summer in the northern hemisphere. Credit: TimeandDate.com

Auroras: What Causes the Northern and Southern Lights

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Auroras occur throughout the year, but the long nights of winter at high latitudes provide an optimal environment in which to see this amazing natural phenomenon.

These colorful patterns of light that dance across the night sky are the result of charged particles from the sun interacting with the Earth’s atmosphere. Originating in a massive explosion on the sun known as a coronal mass ejection, the protons and electrons travel nearly 93 million miles before some of them reach the Earth. When they encounter the planet’s magnetic field, they are pulled toward the poles, where the magnetic force is strongest. There, they interact with atmospheric gases and produce the variety of colors we see. The main factor in which colors are displayed, however, is altitude. Different gases, such as nitrogen and oxygen, vary in concentration at different levels of the atmosphere.

Oxygen molecules can generate green auroras up to 150 miles above sea level and red auroras further up. Nitrogen molecules produce blue lights up to 60 miles above the ground and violet colored lights at higher levels. Auroras, in general, extend from 50 miles to as high as 400 miles above the Earth’s surface.

The word aurora is Latin for dawn. Therefore, the “aurora borealis”, the northern lights, means “dawn of the north”. At the South Pole, the lights are known as the “aurora australis”, which means “dawn of the south”.

Aurora Borealis over Alaska. Credit SmithsonianMag

Perihelion 2018: The Earth is Closest to the Sun Today

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The Earth reached its Perihelion today at 5:34 UTC, which is 12:34 AM Eastern Standard Time. This is the point in the planet’s orbit where it comes closest to the Sun.

This annual event is due to the elliptical shape of the Earth’s orbit and the off-centered position of the Sun inside that path. The exact date of the Perihelion differs from year to year, but it’s usually in early January – winter in the northern hemisphere. The Earth will be furthest from the Sun in July.

While the planet’s distance from the Sun is not responsible for the seasons, it does influence their length. As a function of gravity, the closer the planet is to the Sun, the faster it moves. Today, the Earth is 147.1 million kilometers (91.4 million miles) away from the Sun. That is approximately 5 million kilometers (3 million miles) closer than it will be in early July. This position allows the planet to speed up by about one-kilometer per second. As a result, winter in the northern hemisphere is about five days shorter than summer.

The word, perihelion, is Greek for “near sun”.

Earth is closest to the Sun during the northern hemisphere’s winter. Credit: TimeandDate.com

What the Winter Solstice Means

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Today is the December solstice, the first day of winter in the northern hemisphere. The new season officially begins at 16:28 UTC, which is 11:28 AM EST.

The astronomical seasons, which are different than meteorological seasons, are produced by the tilt of the Earth’s axis – a 23.5° angle – and the movement of the planet around the sun. During the winter months, the northern half of the Earth is tilted away from the sun. This position means the northern hemisphere receives the sun’s energy at a less direct angle and brings us our coolest temperatures of the year.

Since the summer solstice in June, the arc of the sun’s apparent daily passage across the sky has been dropping toward the southern horizon and daylight hours have been decreasing. Today, it will reach its southernmost position at the Tropic of Capricorn (23.5° south latitude), marking the shortest day of the year. This observable stop is where today’s event takes its name. Solstice is derived from the Latin words “sol” for sun and “sisto” for stop.

Soon, the sun will appear to move northward again and daylight hours will slowly start to increase. Marking this transition from darkness to light, the winter solstice has long been a cause for celebration across many cultures throughout human history.

Solstices and Equinoxes. Credit: NASA 

The Supermoon and Other Moon Names

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The first and only supermoon of 2017 will rise on Sunday.

Supermoons are the result of the moon’s elliptical orbit around the Earth. They occur when the moon reaches perigee – its closest point to our planet (less than 223,694 miles). As it is so close, a supermoon looks 7% larger and 16% brighter than an average full moon. When seen near the horizon – where buildings or mountains provide a foreground – an illusion is created that makes the super moon look even bigger. They happen about every thirteen months or so.

When the moon is furthest from Earth – at apogee – it is called a micro-moon.

Full moons occur every 29.5 days when the moon is on the side of the Earth directly opposite the Sun. It reflects the sun’s rays and appears as a beautiful silver disk in the sky.

Ancient civilizations used full moons as a guide to schedule important activities, such as hunting and farming. They gave them each a name based on the dominant weather pattern or typical animal and plant activity during a particular month. In North America, according to National Geographic, native tribes used the moon names listed below. Many are still in use today.

  • January: Wolf Moon or Ice Moon
  • February: Snow Moon
  • March: Worm Moon or Sap Moon
  • April: Sprouting Grass Moon
  • May: Flower Moon
  • June: Strawberry Moon
  • July: Buck Moon
  • August: Sturgeon Moon or Grain Moon
  • September: Harvest Moon
  • October: Hunter’s Moon
  • November: Beaver Moon
  • December: Cold Moon or Long Night Moon

A blue moon is when a second full moon occurs in a single month. Given the uneven nature of our calendar system, these happen roughly every 2.5 years.

The apparent size of the moon as seen from Earth. Credit: KQED