Tiny Voyager spacecrafts put cosmos in perspective

pgeweather@pge.com.July 28, 2012 

Voyager 2, shown above in an artist’s rendering, was launched in 1977 with its sister spacecraft Voyager 1 and is only now leaving the solar system. In 300,000 years, the craft will pass within 25 trillion miles of Sirius, the brightest star in the heavens.

COURTESY PHOTO

Today, I want to look past our local weather toward the heavens. Our galaxy is enormous, on a scale that our souls can understand but our brains cannot. To fully fathom the size of it, consider the summer of 1977, when twin 1,600-pound spacecraft — Voyager 1 and 2 — were launched from the Kennedy Space Center at Cape Canaveral, Fla. NASA’s Jet Propulsion Laboratory in Pasadena designed these spacecraft to take advantage of a 175-year event, when the arrangement of the outer planets allowed these long-distance travelers to slingshot from one planet to the next, picking up speed with each flyby of the planets. Today, after flying for 35 years and moving away from us at roughly 35,000 mph, they are now leaving the solar system and moving into interstellar space about 11 billion miles away.

Radio signals from Voyager 1 take about 16 lighthours to reach the Earth. These modulated radio waves carry a treasure trove of data from visible, infrared and ultraviolet light sensors, along with information from a magnetometer at the end of a 43-foot-long boom. Other instruments include plasma detectors, cosmic ray and charged-particle sensors that scientists from JPL and the California Institute of Technology study closely.

One day, in only 40,000 years, Voyager 1 will fly by a star in the constellation Camelopardalis. In about 300,000 years, Voyager 2 will pass within 25 trillion miles of Sirius, the brightest star in the heavens.

Sirius is also known as the Dog Star because it is the primary star in the constellation Canis Major, the big dog in the southern part of the sky.

After that, the Voyager spacecraft are destined to wander the vast expanse of the Milky Way for a long time.

When Steve Matousek of JPL updated the calculations for these star flybys back in 1989, he thought ahead 300,000 years and realized that he actually would get to accomplish the dream of star travel in a small way.

“I often wonder what Sirius will actually look like from Voyager 1’s perspective when it flies by,” Matousek told me. “You see, Sirius is about twice as massive as the sun and is a binary star system, consisting of a white star and a faint white dwarf companion.”

These frightfully immense numbers only scratch the surface of how big our galaxy really is, not to mention the indigestible distances between the billions of galaxies in the universe.

Despite these enormous distances, scientists have discovered other planets circling other stars in our galaxy. At this time, astronomers have confirmed the existence of more than 600 “exoplanets” outside of our solar system.

When a planet orbits a distant star, the star moves ever so slightly toward and away from Earth in a regular fashion because of gravitational forces between the star and the planet. That’s called a change in radial velocity. The changes in radial velocity make the star’s light spectrum move toward longer wavelengths (red shifted) when it’s moving away, and toward shorter wavelengths (blue shifted) as it moves closer. The same principle can be heard as a train moves toward you and the sound waves are compressed, producing a higher pitched sound. When the train moves away from you, the sound waves become lower pitched. That’s called the Doppler effect.

Leave it to scientists at JPL to try to figure out whether these exoplanets have atmospheres. And if they do, what they are composed of. For example, Earth’s atmosphere is primarily made up of 78 percent nitrogen and 21 percent oxygen. The remaining 1 percent is made up mostly of argon and trace gases such as carbon dioxide.

At this time, none of the exoplanet atmospheres that have been examined look anything remotely like this. However, a planned JPL mission may change this situation.

A NASA spacecraft that’s proposed to launch in 2017 from Vandenberg Air Force Base called FINESSE (the Fast and Exoplanet Spectroscopy Survey Explorer) aims to examine the exoplanet family portrait to see what makes up those atmospheres.

This is how it would work: When planets pass between an observer and a star, they dim the starlight ever so slightly. FINESSE plans to use this technique because the atmosphere of a planet leaves “fingerprints” on the light that arrives at the spacecraft’s telescope.

JPL’s aspiring mission may one day even tell us what the weather is like on these distant planets.

To learn more about the FINESSE mission, please visit http://finesse.jpl.nasa.gov.

Today’s weather report

After a maximum temperature of only 77 degrees Thursday and 85 degrees Friday, high temperatures at the California Mid-State Fair finally cracked into the 90s Saturday. Today’s high temperature at the fair should reach 94 degrees.

Extensive low marine clouds and fog blanket the California coast and even parts of the North County this morning but will quickly clear early this morning from the Mid-State Fair and from the coastal valleys later this morning. The coastal valleys (San Luis Obispo) will reach the low 70s.

Fresh to strong (19- to 31-mph) afternoon northwesterly winds along the coastline will produce temperatures in the mid-60s and clear skies along the westerly facing beaches (Pismo Beach, Grover Beach and Cambria) this afternoon.

The southwesterly facing beaches (Cayucos, Avila Beach and Shell Beach) will reach the high 60s with earlier clearing. The northwesterly facing areas (Morro Bay, Los Osos, Montaña De Oro and the Nipomo Mesa) will see high temperatures range between the high 50s and low 60s with partial afternoon clearing.

Warmer North County and coastal valley temperatures are forecast for Monday, with only subtle changes in the overall synoptic situation expected along the beaches.

Central Coast temperatures will reach seasonal norms especially across the North County from Tuesday through Thursday as a warm high-pressure ridge works its way westward. At the same time, monsoon moisture will filter over the Central Coast with variable mid- to high-level clouds and a chance of thundershowers in the far-eastern regions of San Luis Obispo County and across the Southern Sierra.

The upper-level high-pressure ridge will gradually waken late this week, allowing the marine layer to deepen, with a cooling trend first at locations closer to the coast Friday and across the interior next weekend.

At this time, it appears no excessive heat is in sight except for an outside chance that the warm high-pressure ridge that has resided over the Midwest will move westward during the second week of August.

Today’s surf report

Fresh to strong (25- to 31-mph) northwesterly winds will generate a 3- to 5-foot northwesterly (310-degree deep-water) sea and swell (with a 5- to 9-second period) through Monday.

A 3- to 5-foot northwesterly (295-degree deep-water) swell (with a 7- to 9-second period) will develop along the Pecho Coast on Tuesday and remain at this height and period through Friday. This northwesterly swell will decrease to 2 to 4 feet next weekend. Arriving from the Southern Hemisphere, a 1-foot Southern Hemisphere (200-degree deep-water) swell (with a 20- to 22-second period) will arrive along the coastline Wednesday, building to 1 to 3 feet (with an 18- to 20-second period) Thursday through Friday.

Longer-range models and charts still do not indicate a lot of storm activity in the Southern Hemisphere at this time.

Seawater temperatures

Seawater temperature will range between 53 and 56 degrees through Friday.

Did you know?

PG&E delivers some of the nation’s cleanest electric power. More than half of the electricity the company provides to customers comes from sources that are renewable and/or emit no greenhouse gases. In fact, PG&E’s electricity creates only one-third as many greenhouse gas emissions per kilowatt-hour compared with the industry average.

John Lindsey, media relations representative for PG&E and local weather expert, has lived along the Central Coast for more than 25 years. To subscribe to his daily weather forecast or ask him a question, email him at pgeweather@pge.com.

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